On International CdLS Awareness Day, we recognize the individuals and families affected by Cornelia de Lange Syndrome (CdLS), a rare developmental condition that highlights both the complexity of human genetics and the importance of accurate, timely diagnosis.
CdLS is a genetic disorder typically caused by de novo mutations, meaning the change in DNA occurs early in development rather than being inherited from a parent. It is classified as a cohesinopathy, involving genes that regulate the cohesin complex, an essential system for chromosome structure, gene expression, and normal development.
A Spectrum Rooted in Genetics
CdLS presents as a spectrum, with a wide range of clinical features that can include differences in growth, limb development, cognition, and organ systems. Because of this variability, diagnosis can sometimes be delayed, particularly in milder cases.
The condition is estimated to occur in approximately 1 in 10,000 live births, though this is likely an underestimate due to underdiagnosis (CdLS Foundation). The most commonly implicated gene is NIPBL, with additional contributions from genes such as SMC1A, SMC3, RAD21, and HDAC8 (MedlinePlus Genetics, 2024). While genetic testing identifies a causative variant in about 80% of cases, making a strong argument for genetic screening, clinical expertise remains essential for an accurate diagnosis.
Why De Novo Detection Matters
Because CdLS is most often caused by de novo variants, identifying the causative mutation requires careful comparison between a child and their parents. This is where trio-based genomic analysis becomes especially powerful. By analyzing sequencing data from the affected individual alongside both parents, clinicians can:
- Pinpoint new (de novo) variants
- Filter out inherited background variants
- Prioritize variants in genes known to impact development
This approach has become a cornerstone of rare disease diagnostics, significantly increasing diagnostic yield compared to single-sample analysis (Wright et al., Nature Reviews Genetics, 2018; Stark et al., Genetics in Medicine, 2019).
Supporting Rare Disease Diagnosis with VarSeq
Tools like VarSeq are widely used to support trio analysis workflows, helping labs efficiently identify de novo variants that may underlie conditions like CdLS. With VarSeq, users can:
- Apply inheritance-based filtering to rapidly isolate candidate de novo variants
- Prioritize variants in clinically relevant genes such as NIPBL and related cohesin genes
- Integrate phenotype-driven analysis to connect genomic findings with clinical presentation
In conditions where the causal variant may be rare, subtle, or unexpected, these capabilities can help reduce the time to diagnosis, providing clarity for clinicians and, importantly, answers for families.
Moving Forward with Awareness and Precision
For families affected by CdLS, a diagnosis is more than a label, it’s a pathway to understanding, care, and community. Continued awareness, combined with advances in genomic analysis, is helping make that path clearer.
On this International CdLS Awareness Day, we at Golden Helix recognize the importance of early detection, accurate genetic interpretation, and compassionate clinical care, and the role that modern genomic tools play in supporting all three. For more information about how VarSeq can be used in rare disease detection, please see our Webinar on single sample and family based genome analysis, or reach out to us a [email protected].
Further Resources for Cornelia de Lange Syndrome
U.S. National Library of Medicine. (2022, April 13). Cornelia de Lange Syndrome: Medlineplus genetics. MedlinePlus. https://medlineplus.gov/genetics/condition/cornelia-de-lange-syndrome/
What is CdLS?. CdLS Foundation. (2025, June 12). https://www.cdlsusa.org/what-is-cdls/
Wright, C. F., FitzPatrick, D. R., & Firth, H. V. (2018). Paediatric genomics: Diagnosing rare disease in children. Nature Reviews Genetics, 19(5), 253–268. https://doi.org/10.1038/nrg.2017.116
Stark, Z., Dolman, L., Manolio, T. A., Ozenberger, B., Hill, S. L., Caulfied, M. J., Levy, Y., Glazer, D., Wilson, J., Lawler, M., Boughtwood, T., Braithwaite, J., Goodhand, P., Birney, E., & North, K. N. (2019). Integrating genomics into healthcare: A global responsibility. The American Journal of Human Genetics, 104(1), 13–20. https://doi.org/10.1016/j.ajhg.2018.11.014
